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# Powers of Ten

In physics, math, and engineering, we often express numbers by powers of ten. We will meet these terms again, e.g. in Giga-Hertz (GHz), Centi-meters (cm), Micro-seconds (s), and so on.

Powers of Ten
Nano 10-9 1/1000000000 n
Micro 10-6 1/1000000 μ
Milli 10-3 1/1000 m
Centi 10-2 1/100 c
Kilo 103 1 000 k
Mega 106 1 000 000 M
Giga 109 1 000 000 000 G

Knowing the speed of light, we can calculate the wavelength for a given frequency. Let us take the example of the frequency of 802.11b wireless networking, which is

f = 2.4 GHz = 2,400,000,000 cycles / second

wavelength lambda (λ) = c / f

= 3*108 / 2.4*109
= 1.25*10-1 m
= 12.5 cm

Frequency and wavelength determine most of an electromagnetic wave's behaviour, from antennas that we build to objects that are in the way of the networks we intend to run. They are responsible for many of the differences between different standards we might be choosing. Therefore, an understanding of the basic ideas of frequency and wavelength helps a lot in practical wireless work.

Last Update: 2010-12-02